As an apparatus for dispensing various types of liquid materials in units of a predetermined amount, the so-called “dispenser” is known which includes a container storing the liquid material, and which discharges the liquid material in units of the predetermined amount from a nozzle connected to the container by the action of pneumatic pressure or mechanical pressure.
When trying to discharge, among various types of liquid materials to be discharged by the dispenser, particularly a liquid mixed with solid particles having greater specific gravity than the liquid, there occurs a phenomenon that, with the lapse of time, the solid particles precipitate on the bottom of a container, or aggregate in the vicinity of a nozzle opening. To prevent such a phenomenon, the liquid has to be stirred to keep a state where the solid particles are uniformly mixed in the liquid.
The stirring is generally practiced by disposing a stirrer in association with the container. However, when a discharge mechanism including a nozzle cannot be disposed in union with or near the container and the discharge mechanism is spaced from the container, the solid particles may precipitate midway a pipe connecting the container and the discharge mechanism, and a sufficient effect cannot be obtained with the stirring inside the container in many cases. As another stirring method used to cope with the above-mentioned problem, there is a method of forming a circulation path between the container and the discharge mechanism, and keeping the liquid in a state always flowing in the circulation path.
For example, Patent Document 1 discloses a circulation-type liquid material discharge device including a container that stores a liquid material, a means that stirs the liquid material in the container, and a looped piping through which the liquid material in the container is always circulated, a pump that is disposed in the looped piping and that feeds the liquid material under pressure, a nozzle that has a discharge opening, and a valve that opens and closes communication between the looped piping and the nozzle, wherein the valve includes a substantially linear flow path that constitutes a part of the looped piping and that extends substantially horizontally, a valve seat that is formed in an inner wall surface of the flow path at the lower side thereof, the valve seat being formed such that the vicinity of the valve seat is not positioned at a level lower than the inner wall surface of the flow path around the valve seat and that the valve seat is positioned at a level higher than the lowest end of the inner wall surface of the flow path, and a lift valve formed such that a tip of the lift valve is movable to cross the flow path and come into contact with the valve seat, thus opening and closing communication between the flow path and the nozzle.
Patent Document 2 discloses an ink jet nozzle including a nozzle hole through which ink is discharged, an ink chamber from which the ink under pressure is supplied to the nozzle hole, a needle valve that is disposed in the ink chamber and that opens and closes the nozzle hole, a driving mechanism that drives the needle valve, a driving-mechanism accommodating space that accommodates the driving mechanism, and an elastic diaphragm that isolates the ink chamber and the driving-mechanism accommodating space from each other, the driving-mechanism accommodating space containing gas or a liquid that is subjected to pressure comparable to the pressure applied to the ink in the ink chamber, wherein an ink tank under pressure is connected to the ink chamber through a circulation path, and the ink is circulated by employing a pump.